PATH 12 - OCD explanations 3 and treatments 1

Question 1

What is the neural explanation for OCD?

Answer 1

The view that physical and psychological characteristics are determined by the behaviour of the nervous system, in particular the brain as well as individual neurons

Question 2

What is the COMT gene?

Answer 2

• Involved in the production of dopamine
• One type of this gene = higher levels of dopamine

Question 3

What is the SERT gene?

Answer 3

• Involved in the transmission of serotonin
• One type of this gene = lower levels of serotonin

Question 4

What is a neurotransmitter?

Answer 4

• Brain chemicals released from synaptic vesicle that relay signals across the synapse from one neurone to another
• Neurotransmitters can be broadly divided into those that perform an excitatory function and those that perform an inhibitory function

Question 5

What is excitation?

Answer 5

• When a neurotransmitter, such as adrenaline or dopamine, increases the positive charge of the postsynaptic neuron
• This increases the likelihood that the postsynaptic neuron will pass on the electrical impulse

Question 6

What is inhibition?

Answer 6

• When a neurotransmitter, such as serotonin or GABA, increases the negative charge of the postsynaptic neuron
• This decreases the likelihood that the postsynaptic neuron will pass on the electrical impulse

Question 7

What is the role of serotonin in OCD?

Answer 7

• One explanation of OCD concerns the role of the neurotransmitter serotonin
• Serotonin is a neurotransmitter that helps regulate mood
• Neurotransmitters are responsible for relaying information from one neuron to another
• If a person has low levels of serotonin, then normal transmission of mood-relevant information does not take place, and a person may experience low moods (and other mental processes may also be affected)
• Only some cases of OCD may be explained by a reduction in the functioning of the serotonin system in the brain

Question 8

What is the role of the frontal lobe in OCD?

Answer 8

• Some cases of OCD and in particular hoarding disorder, seem to be associated with impaired decision making which may be associated with the abnormal function of the lateral (side bits) of the frontal lobe
• The frontal lobes are the front part of the brain that are responsible for logical thinking and decision-making
• It is also linked to obsessions and compulsions

Question 9

Why might the frontal lobe be functioning abnormally in OCD?

Answer 9

• Disrupted serotonin system
• Physical damage to structure of frontal lobes
• Genetic mutation

Question 10

What is the role of the parahippocampal gyrus?

Answer 10

• Associated with processing unpleasant emotions e.g. fear and anxiety, and reduces unpleasantness
• May function abnormally in OCD so unpleasantness is not reduced leading to obsessive thinking which triggers compulsive behaviours

Question 11

Why might the parahippocampal gyrus be functioning abnormally in OCD?

Answer 11

• Disrupted serotonin system
• Physical damage to structure of parahippocampal gyrus
• Genetic mutation

Question 12

What are the strengths of the neural explanation for OCD?

Answer 12

Research support

Question 13

What research support is there for the neural explanation for OCD?

Answer 13

• One strength of the neural model of OCD is the existence of some supporting evidence
• Antidepressants that work purely on serotonin are effective in reducing OCD symptoms and this suggests that serotonin may be involved in OCD
• Also, OCD symptoms form part of conditions that are known to be biological in origin, such as the degenerative brain disorder Parkinson’s disease, which causes muscle tremors and paralysis (Nestadt et al. 2010)
• If a biological disorder produces OCD symptoms, then we may assume the biological processes underlie OCD
• This suggests that biological factors (e.g. serotonin and the processes underlying certain disorders) may also be responsible for OCD

Question 14

What are the limitations of the neural explanation for OCD?

Answer 14

The serotonin-OCD link may not be unique to OCD

Question 15

What is the issue with serotonin-OCD link?

Answer 15

• One limitation of the neural model is that the serotonin-OCD link may not be unique to OCD
• Many people with OCD also experience clinical depression
• Having two disorders together is called co-morbidity
• This depression probably involves (though is not necessarily caused by) disruption to the action of serotonin
• This leaves us with a logical problem when it comes to serotonin as a possible basis for OCD
• It could simply be that serotonin activity is disrupted in many people with OCD because they are depressed as well
• This means that serotonin may not be relevant to OCD symptoms